Short answers, pulled from the story.
GameRankings was founded in 1999 and owned by CBS Interactive. The site operated as a silent architect that collected and linked to scores from hundreds of other websites and magazines without hosting a single review itself.
GameRankings translated disparate scoring systems into a unified percentage using a simple mean of every ranking from all accredited websites. The site converted scores from 5 or 10 point scales and letter grades into percentages to maintain a consistent scale for comparison.
A game did not receive a ranking until it accumulated six total reviews to ensure the score was statistically significant. This threshold prevented the score from being skewed by a small number of outliers and allowed for comparison against other games in the database.
Super Mario Galaxy, The Legend of Zelda: Ocarina of Time, Super Mario Odyssey, Super Mario Galaxy 2, The Legend of Zelda: Breath of the Wild, Grand Theft Auto IV, and Grand Theft Auto V stood as the pinnacle of critical acclaim. These titles held an aggregate score of 97% or higher at the time of the site's closure in December 2019.
GameRankings was shut down and redirected to Metacritic on the 9th of December 2019. The discontinuation resulted from a strategic decision by CBS Interactive to merge its staff with the similar aggregator Metacritic to consolidate resources and streamline operations.